Adaptive formation control of autonomous underwater vehicles with model uncertainties

This paper investigates the formation control problem of underactuated autonomous underwater vehicles (AUVs). What makes this problem different and challenging is that, in the AUV model, the mass and damping matrices are not diagonal with nonzero off-diagonal terms and unknown hydrodynamic damping terms. To address the effect of nonzero off-diagonal terms, we introduce a coordinate transformation, while the unknown hydrodynamic damping terms are approximated adaptively by a neural network. Then, a leader-follower control strategy is presented, where each follower needs to track a virtual vehicle. This strategy translates the formation control problem into a set of position (including heading) tracking problems for the following AUVs. The position and heading tracking controller is designed based on Lyapunov direct method and backstepping technique, taking into account the effect of the nonzero off-diagonal terms in the mass matrix and the unknown hydrodynamic damping terms. Simulations are given to demonstrate the effectiveness of the control method proposed.